1. Field of the Invention
The inventive concepts disclosed herein generally relate to well tubing handling systems, and more particularly, but not by way of limitation, to an apparatus for absorbing force for a top drive assembly used to rotate a drill string.
2. Brief Description of Related Art
It is known in the petroleum industry to use top drive systems to rotate a drill string to form a borehole. Top drive systems are equipped with a motor to provide torque for rotating the drill string. Top drive systems are capable of being raised and lowered along a substantially vertical axis directly above the borehole. Additionally, a length of drill pipe is connected to the top drive system so as to extend downwardly therefrom in a substantially vertical direction, and a drill bit is secured to the downward end of the drill pipe.
When drilling a borehole, the top drive system is activated so as to rotate both the drill pipe and the drill bit at the desired speed. Then, the top drive system, together with the drill pipe and bit, is lowered. When the drilled hole is deep enough to accommodate the first length of drill pipe, the top drive system is disconnected from the drill pipe and raised to its original position. A second length of drill pipe is then connected between the top drive system and the first length of drill pipe, thereby increasing the effective length of the drill string. Thereafter, the top drive system is again activated, and the drilling operation is continued. This procedure is then repeated until the desired hole depth is achieved.
One of the problems encountered during the process of adding additional joints of drill pipe is that the weight of the top drive system and a joint of pipe suspended from the top drive assembly results in a significant force being applied to the threads as the new joint of drill pipe is stabbed into, or otherwise brought into engagement with, the top end of the joint to which it is desired to make a connection. This significant force can result in damage to the threads of the drill pipe, thereby increasing the costs due to downtime and costs associated with repairing the threads of the drill pipe.
To this end, a need exists for an apparatus that can absorb the force between a top drive assembly and an adjacent joint of pipe so as to alleviate damage to one or both. It is to such an apparatus that the present invention is directed.